Cartridge fuse



July 7, 1953 L. DETcH 2,644,871

CARTRIDGE FUSE Filed Oct. 2, 1951 l Ellglml b4 Ay l26 all 57 i I WA-553W Patented July 7, 1953 UNITED STATES PATENT OFFICE Lewis Detch, Pittsburgh, Pa. Application October 2, 1951, Serial No. 249,297

4. Claims. (Cl. 20G-131) This invention relates to electric circuit breakers, particularly thermal circuit breakers and more especially to fusible element circuit breakers.

A principal object of this invention is to provide a two part knife blade renewable cartridge fuse which will effectively dispose of hot metal and gases resulting from blowing 4of the fuse.

Other objects and advantages will appear as the description of the particular physical embodiment selected to illustrate the invention progresses and the novel features will be particularly pointed out in the appended claims.

In describing the invention in detail andthe particular physical embodiment selected to illustrate the invention, reference will be had to the accompanying drawings and the several views thereon, in which like characters of reference designate like parts throughout the several views, and in which:

Fig. 1 is an elevational View of a complete cartridge knife blade fuse constructed in accordance with my invention; Fig. 2. is a view of the device of Fig. 1 viewed from below, as shown in Fig. 1, and showing the cartridge and ferrule in section; Fig. 3 is a View likeFig. 1 except that the ferrules and cartridge are shown in section; Fig. 4 is a cross sectional view on the plane indicated by the line IV-IV of Fig. 3, viewed in the direction of the arrows atthe ends of the line; Fig. 5 is a cross sectional view of the device as shown by Fig. 4 on the plane indicated by the line V-V viewed in the direction of the arrows at thevends of the line; and Fig. 6 is a View similar to Fig. 5` but illustrating a modified form of the device.

The main body I of my device is made of tubular insulating material, preferably, horn or fibre. The tubular member I is formed with external threads, as 2, on each end thereof.

Two hollow internal screw-threaded ferrules 3 and 4 are used with my invention, one is attached to one end of the tubular member I and the other is attached to the other end. Each ferrule has an internal thread, as 5, which cooperates with the thread 2 of the tubular member I. Each ferrule is formed with a stop shoulder, as 6, which limits and positions the ferrule on the end of the tubular member I..

In addition to the screw-threaded engagement y between the tubular member I and the ferrules, I

prefer to also use a plurality of rivets, as 'I, with each ferrule. Each of these rivets passes through the ferrule and through the wall of the tubular member I, and is upset or riveted on each end as shown at 8 and 9,.

The ferrule 3 is formed with three internal diameters, the internal diameter I0, the internal diameter II and the internal diameter I2. Those forming the interior of the ferrule 3 leave shoulders at I3 and at I4. The smallest internal diameter is I0, the next larger is II and the largest is I2.

The ferrule 4 is formed with internal screwthreads I5 in its portion of largest internal diameter. The screw-threads extend only for a denite distance in the portion of largest internal diameter, then a groove I6 is formed between the ending of the threads and the portion l'I of smaller internal diameter leaving a shoulder at I8. l

Partly Within and partly without the tubular member and the ferrules is a fuse strip carrier and knife blade assembly designated as a Whole by A.

The device includes two knife blades I9 and 20. Each knife blade is rectangular in shape and is formed with a tang, as 2 I, which is also substantially rectangular in shape. The provision of a tang on the knife blades leaves shoulders as at 22 and 23.

The tangs 2I and 24 are connected by an insulating spacer bar 25. They are also connected by the fuse strip 26. Suitable means are provided for passing through the spacer bar, the tangs and the fuse strip to hold all together. The form shown is a headed bolt, as 21, with a nut, as 28,

von one end thereof. Pins, as 29, are also passed through the insulating spacer bar and the tang to prevent the knife blades and the insulating spacer bar from getting out of alignment.

On tang 2I a disc 38 is positioned. This disc is between the shoulders 22 and 23 and the end of the spacer bar 25 and is held in place against the shoulder by distorting the metal of the tang at 3| and 32 Vas by a chisel so as to hold the disc 30 in place. The disc 33 has three diameters 33, 34 and 35. The smallest diameter substantially lits the smallest diameter I3 of the ferrule 3. The diameter 34 substantially ts the diameter II of the ferrule 3. The diameter 35 substantially fits the diameter I2 of the ferrule 3.

When the fuse strip assembly is in place, the outer facev 33 ofthe largest diameter portion 35 of the disc 30 bears tightly against the shoulder I3.

Tang 24 carries a disc 31, the outer face of which bears against the shoulders of knife blade 2i) similar to the shoulders 22 and 23 of knife blade I9. The disc 31 has a circular depression 38 opening in the innerface thereof and within this circular depression is a disc 39. The disc 39 has a slot therethrough aligning with a like 3 slot in the disc 31 through which the tang 24 of the knife blade 2li passes. The two discs are held firmly against the shoulders oi knife blade by distorted metal of the tang as at 49 and 4l, distorted as by a cold chisel.

The disc 31 is of such thickness that when its outer face is flush with the outer edge of the ferrule 4, the inner face fails to reach the shoulder I3.

The disc 31 is formed with slits as 42 and d3. These slits which I call partial slits, extend only a short distance toward the center of the disc 31, as best shown in Figs. 4 and 5. I have shown only two slits on my preferred form, but l may have a plurality of slits as t4, 45, and 41 as shown in the modified form, 6.

Through vent bores as i8 and 45! are formed from the outer face oi the disc 31 to the slits A2 and 43.

The fuse strip carrier and knife blade assembly A may be removed as a unit from the member l. This is done by exerting torque on a knife blade, to turn disc 3l so that it will screw out from the ferrule il. When 3l has been unn screwed sufficiently, then the remainder of the operation is merely to withdraw all of the ren maining parts from the tubular member. When this has been done, the fusible strip 26 may be renewed and the parts returned to the original position by sliding the assembly into the tubular member and then rotating it so that the member 3l screws into the ierrule Ll until face 33 bears iirinly against shoulder I3. When this has been done, the member is still positioned away `from shoulder lll because the distance from shoulder i8 to shoulder i3 is less than the distance from outer face til to the inner face ol disc 'li/ly construction is such that the hot gases and vaporised metal which generated when a fuse blows may issue well cooled from the right hand ond oi' the iuse as shown in lig, 2. The hot vaporized metal and gases first pass by the largest diameter of the disc 3f) and are somewhat obstructed by shoulder I3 and then pass along the next smaller diameter of disc 3l), that is, along E i and then are somewhat stopped by if; and then pass out along the smallest diameter 1.3 oi the disc These several steps the vapors and gases to be so throttled and cooled down, especially in passing by the shoulder lil where there is a close contact be tween the disc and the shoulder, that when they issue tothe atmosphere, they are soV cool that they will not ignite readily ignitable material closely adjacent to the fuse. The tortuous re stricted path accentuated by the pressure contact at shoulder l5 is very eiiicient in properly and effectively handling the hot vapors and gases.

At the other end of fuse, that is, at the leit hand end shown in Fig. 2, the hot metallic vapors and gases have several means ol' issuing from the interior oi the cartridge fuse. Some of the vapors may pass out along the thread l5. is contemplated that the fit ol' the threads at this point will be such that after the gases have arrived at the slits as ft2 and 63, they pass into those slits and then turn out through the vents as This path is a long path as it follows the screwthreads several times around the internal surface oi' the ferrule.

'in addition to 'the other path at the left hand end of the fuse, the vapors may issue through the very highly restricted passages between the tang of the knife blade and the discs 31 and 39.

In addition to the other paths for the gas to issue from the left hand end oi the fuse, there is the path along the periphery of the disc 39 and then along the contacting surface between disc 3Q and disc 31 and then along the tang 24 of the knife blade 2U.

The partial slits 42 and 43 are quite effective in preventing the hot metallic vapors from freezing or soldering the disc 31 to the `ferrule 4. The vapors and gases are shunted from the thread l5 after they have passed only a portion of the way along them so that they have not been sufficiently cooled to cause disc 3l to be soldered to ierrule 4 so that my screw-threaded connection at the lei't hand end of the cartridge fuse is an improvement of such a nature that it makes the connection operative whereas without the slits such a connection would be inoperative due to the soldering effect.

The slits i2 and lii not only greatly assist in the venting of the ius-e but they also appear to have an indicating effect, that is, in screwing the knife blade and fuse strip assembly into place, proper tension thereof is more properly sensed by the hand when the slits 42 and are present than when they are absent. There seems to be a sort ci elastic response that would not otherwise be present.

Although l have particularly described one particular physical embodiment of invention and explained the construction and principle thereof, nevertheless, l desire to have it understood that the form selected is merely illustrative, but does not exhaust the possible physical embodiments of the idea of means underlying` my invention.

What I claim as new and desire to secure by Patent is:

l. -A renewable cartridge fuse, comprising, in combination, a tubular casing of insulating material, hollow metallic ferrules, one permanently affixed on each end of the casing, one ferrule formed at its outer end with portions having three internal diameters forming two internal shoulders one of which is innermost, the other ferrule formed with portions of two internal diameters, the portion nearest the outer end of the ferrule having the larger diameter and formed with an internal screw thread, the thread stopping short of the smaller internal diameter portion, the material of the errule being removed to the depth of the screw-thread between the ending oi the thread and the beginning of the portion o1` smaller internal diameter thereby forming a groove and a shoulder, a fuse strip carrier and knife blade assembly positioned partly wthin and partly without the tubular casing, including a spacer bar of insulating material, two metallic knife blades, one at each end of the spacer bar, each knife blade formed of two rectangular portions, one narrower than the other forming a tang and a shoulder, one tang contacting one end of the spacer bar and the other tang contacting the opposite end of the spacer bar, a fuse strip extending between the tangs and parallel to the spacer bar, means for connecting the spacer' bar, fuse strip, and tangs, a disc formed with a through slot adapted to receive a tang positioned on one knife blade between the end of the spacer bar and the shoulder of the knife blade, distorted metal of the tang abutting one side of the disc for holding it in place against the shoulder, said disc formed with three diameters, the smallest, substantially the same as the smallest internal diameter of the said one ferrule, one diameter substantially that of one of the other two internal diameters of the same said one ferrule and one substantially that of the other two internal diameters of the said one ferrule, a second disc on the tang of the other knife blade, said second disc abutting the shoulder thereof, said second disc formed with an external screw thread fitting the screw thread in the said other ferrule and being of a thickness such that when the outer end is flush with the outer end of the internally screw-threaded ferrule the inner end terminates short of the internal shoulder of the screw-threaded ferrule, said second disc formed with a circular depression in the face adjacent the spacer bar, a third disc positioned in and substantially filling said depression, both the second named disc and the third named disc formed with through slots, in line one with the other, said slots receiving the tang of the knife blade, distorted metal of the tang labutting the third named disc holding it in place, said second named disc formed with partial slits transverse thereof, said slits opening in the-edge of the disc bearing the thread and vent holes, one extending from the outer face of the second named disc to each of the slits, the distance between the innermost shoulder on the said one ferrule and the shoulder at the groove on the said other ferrule, being less than the distance between the inner face of the second named disc and the outer face of the largest diameter portion of the first named disc,

2. A renewable cartridge fuse cartridge, comprising, in combination, a tubular casing of insulating material, hollow metallic ferrules, one permanently affixed on each end of the casing, one ferrule formed at its outer end with portions having three internal diameters forming two internal shoulders one of which is innermost, the other ferrule formed with portions of two internal diameters, the portion nearest the outer end of the ferrule having thelarger diameter and formed with an internal screw-thread, the thread stopping short of the smaller internal diameter portion, the material of the ferrule being removed to the depth of the screw-thread between the ending of the thread and the beginning of the portion of smaller internal diameter thereby forming a groove and a shoulder.

3. A fuse strip carrier and knife blade assembly, including, a spacer bar of insulating material, two metallic knife blades, one at each end of the spacer bar, each knife blade formed of two rectangular portions, one narrower than the other forming a tang and a shoulder, one tang contacting one end of the spacer bar and the other tang contacting the opposite end of the spacer bar, a fuse strip extending between the tangs and parallel to the spacer bar, means for connecting the spacer bar, fuse strip, and tangs, a disc formed with a through slot adapted to receive a tang positioned on one knife blade between the end of the spacer bar and the shoulder of the knife blade, distorted metal of the tang abutting one side of the disc for holding it in place against the shoulder, a second disc on the tang of the other knife blade, said second disc abutting the shoulder thereof, said second disc formed with an external screw-thread, said second disc formed with a circular depression in the face adjacent the spacer bar, a third disc positioned in and substantially filling said depression, both the second named disc and the third named disc formed with through slots, in line one with the other, said slots receiving the tang of the knife blade, distorted metal of the tang abutting the third named dise holding it in place, said second named disc formed with partial slits transverse thereof vand intermediate the end faces of the disc, said slits opening in the edge of the disc bearing the thread, and vent holes, one extending from the outer face of the second named disc to each of the slits.V

4. A renewable cartridge fuse, comprising, in combination, a tubular casing of insulating material, hollow metallic ferrules, one permanently axed on each end of the casing, one ferrule formed with a shoulder facing inwardly, the other ferrule formed with a shoulder facing outwardly and with an internal screw thread outwardly of the shoulder, a fuse strip carrier and knife blade assembly positioned partly within and partly without the tubular casing, including a spacer bar of insulating material, two metallic knife blades, one at each end of the spacer bar, each knife blade formed of two rectangular portionsy one narrower than the other forming a tang and a shoulder, one tang contacting one end of the spacer bar and the other tang contacting the opposite end of the spacer bar, a fuse strip extending between the tangs and parallel to the spacer bar, means for connecting the spacer, fuse strip, and tangs, a disc on one tang between the end of the spacer bar and the shoulder of the knife blade, distorted metal of the tang abutting one side of the disc for holding it in place against the shoulder, said disc formed with a shoulder adapted to abut the shoulder facing inwardly on said one ferrule, a second disc on the tang of the other knife blade, rneans to hold the disc against the shoulder of the knife blade, said second disc formed with an external screw thread tting the screw thread in the said other ferrule, the distance between the shoulder facing inwardly on said one ferrule and the shoulder on the said other ferrule being less than the distance between the inner face of the second named disc and the face of the first named disc adapted to abut the shoulder facing inwardly of the said one ferrule.

LEWIS DETCH.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,559,890 La Mar Nov. 3, 1925 1,773,184 Hickey Aug. 19, 1930 1,831,002 Hickey Nov, 10, 1931 2,195,147 Griffith Mar. 26, 1940 2,497,227 Messer et al Feb. 14, 1950 

